This invention relates generally to a magnetic levitation vehicle system, and more particularly concerns a system for electrical power storage and delivery by a maglev vehicle such as a maglev train.
The demand for electric power from regional power grids is not constant, but varies substantially with time. Typically, power demand is low during the night time, increasing substantially during the day, as illustrated in FIG. 1. Much of the time, electrical grids experience two distinct peak demand periods, the first in the morning and the second in the afternoon. Power demand also varies considerably with the day of the week, being higher during the Monday to Friday period, and lower on weekends. It also varies considerably with the seasons, with the summer demand usually being substantially higher than during the rest of the year.
It would be expensive, and technically difficult to have coal and nuclear power plants go up and down in power output to meet the fluctuating load demand. Instead, peaking power is generally supplied either from combustion fired low capital cost units (e.g., turbines or combined cycle plants), or from energy storage units that take in surplus power from baseload plants during low power demand periods and return it to the grid during high demand periods. Presently, spinning reserve is provided by keeping expensive generator units hot and ready to generate large blocks of power in a very short notice.
FIG. 2 shows the current leading conventional options for peaking power. Of the present energy storage options, only pumped hydroelectric power (pumped hydro) is used to any extent. Batteries, flywheels, and superconducting energy storage (SMES) are too expensive to be practical. While pumped hydro can be practical in terms of cost, its environmental and siting problems severely constrain its usefulness.
Existing technologies for electrical power storage, such as batteries, flywheels, and superconducting energy storage (SMES) are generally too expensive and difficult, or too limited in siting, such as pumped hydro. To be useful, the great majority of peak power demand is supplied by fossil fueled peaking power plants—e.g., gas turbine—or by purchase from distant power grids. Such power generating units generally use oil or natural gas fuel. In fact, many units are designed so that they can burn either fuel, and switch back or forth depending on which is cheaper at a given point in time. The long term outlook for oil and natural gas prices is a continual increase, which will cause further hikes in the cost of peak power.
The cost of supplying peaking power can be high. For California in August of 2000, peak prices of about $500 per MWH (50 cents per KWH) were paid during this period, prior to a state cap of about $250 per MWH (25 cents per KWH) imposed on Aug. 17, 2000. The peak cost is a factor of 10 greater than the minimum cost, which would apply during low demand periods, e.g., night time. This large differential, and the high cost of peak power, provides a major opportunity for a low cost energy storage system. By buying low cost power at night storing it, and delivering it during the day at peak power rates, a low cost storage system could be more efficient and economical. An energy storage system that could store large amounts of electric power for a few cents per KWH would enable cost savings of hundreds of billions of dollars annually over the world.
The cost of wind generation of electricity was once seen as prohibitive, but is now becoming more competitive. Wind generation of electricity produces no emissions, is renewable, and is one of the cleanest sources of electricity. The same is true for solar generation of electricity. However, until an adequate electrical power storage technology can be developed, utilities can not rely on wind or solar generated electricity for peaking power requirements. While wind and solar generation of electricity account for a small fraction of the nation's electricity, and can be intermittent and unpredictable, with an adequate electrical power storage technology, wind and solar energy could be used to generate electrical power that could be stored for introduction into the power grid as needed. It thus would be desirable to provide a new energy storage technology that can provide a low cost, near term method of storing large amounts of electrical energy and delivering it rapidly and in the amounts needed to the grid. The present invention addresses these and other needs.